Browsing by Author "Valero, M"

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    Development of microsatellites DNA markers in the cultivated seaweed, Gracilaria chilensis (Gracilariales, Rhodophyta)
    (2005) Guillemin, ML; Destombe, C; Faugeron, S; Correa, JA; Valero, M
    The red algae Gracilaria chilensis is extensively cultivated for agar production. In spite of its commercial significance as the first algal resource in Chile, no information is available on the pattern of genetic diversity. In this paper, we isolated six polymorphic microsatellite markers from a G. chilensis-enriched DNA library. Genetic diversity was assessed in two natural populations revealing relatively low levels of heterozygosity ranging from 0.00 to 0.51. The six loci developed here are good candidates to assess the level of genetic resources within this species, which probably suffered from over-exploitation in several localities along the Chilean coast.
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    Hierarchical spatial structure and discriminant analysis of genetic diversity in the red alga Mazzaella laminarioides (Gigartinales, Rhodophyta)
    (2001) Faugeron, S; Valero, M; Destombe, C; Martínez, EA; Correa, JA
    Our study of the genetic structure of Mazzaella laminarioides (Bory) Fredericq (Gigartinales) in the central Chilean region documented a high level of genetic diversity based on random amplified polyp morphic DNA (RA-PD) markers and indicated the occurrence of significant genetic structure at different spatial scales. A total of 288 haploid gametophytes was analyzed with 17 polymorphic RAPD bands, which produced 202 distinct multilocus genotypes. Within stands, mean gene diversity ranged from 0.210 to 0.249 and no significant linkage disequilibrium could be detected among pairs of alleles, revealing that recombination (sexual reproduction) regularly shuffles the genes at that scale. Analysis of molecular variance within stands (less than 30 in) showed that the structure was very low, only marginally significant, and did not increase with increasing hierarchical levels at this lowest spatial scale. In contrast, at a larger spatial scale (among stands, from 5 to 60 km), increasing geographical distance seemed to account for increasing isolation between populations even if natural barriers, such as sandy beaches or river estuaries, may play a role in such isolation. Moreover, the strong genetic differentiation occurring between locations separated by 60 kin allowed the assignment of individuals to their original population through a canonical discriminant analysis. This approach further allowed the identification of potential recent migrants from one population to the other. Thus, in species like M. laminarioides for which the dominance of RAPD markers can be avoided by selecting haploid individuals, RAPD analysis appeared to be specially appropriate for the study of genetic differentiation.
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    Reduced genetic diversity and increased population differentiation in peripheral and overharvested populations of Gigartina skottsbergii (Rhodophyta, Gigartinales) in southern Chile
    (2004) Faugeron, S; Martínez, EA; Correa, JA; Cardenas, L; Destombe, C; Valero, M
    This study assesses two hypotheses on the genetic diversity of populations of Gigartina skottsbergii Setchell et Gardner (Rhodophyta, Gigartinales) at the border of the species distribution: 1) peripheral populations display a reduced genetic diversity compared with central populations, and 2) genetic differentiation is higher among peripheral than among central populations. Two peripheral and four central populations were sampled along the Chilean coast and 113 haploid individuals were analyzed using 17 random amplification of polymorphic DNA loci. The genetic diversity was estimated by allele diversity (H-e), allele richness (A), and the mean pair-wise differences among multilocus genotypes. All three estimates consistently and significantly indicated a lower genetic diversity within the peripheral than within the central populations. Genetic differentiation between the two peripheral populations was stronger (F-ST=0.35) than between central populations at similar spatial scales (F-ST ranging from 0 to 0.25). In addition, it appeared from the distribution of pair-wise differences that peripheral populations are in demographic expansion after a recent bottleneck. The results are discussed in the specific context of potential overharvesting of these wild populations.